Question
For several months now we have been hearing "something" underneath the house. Sounds vary. They range from what sounds like something rustling to throwing up. I have twice gone under the house and could not find anything. The space between the house and the ground has been bricked up with the exception of a repeating pattern of vent spaces (4 holes the width and height of a single brick every 15' or so). I have dusted with flour every spot where there is an opening of any size to see if the flour is disturbed by the animal's coming and going. No dice; never disturbed.  I have seen a big fat Opossum around the house twice, but much to big for the vent openings. But still I figure it has to be the culprit. I have placed a humane trap under the house with smelly fish as bait too, left in place for weeks and still nothing. My latest foray into this is to drop cat urine litter balls close to where the sound comes from. Do you thing this will have any effect or do you have a better solution other than calling the pest control to kill whatever is under there. Second question, I have squirrels in the attic, but I'm quite lucid. Seriously, with the coming heat will that drive them out and then can I seal up my attic vents with wire mesh? Would cat urine work here? Or do I need to squeeze myself into this nearly inaccessible place and manually remove them.

Answer
You are missing something. Visit http://icwdm.org for proper inspection techniques.

Remember, raccoons only need a 4" inch diameter hole. Gray squirrel 3 inches, rat one inch. House mouse 3/8th of an inch.

Don't waste your time with cat urine or other repellents. detials on why they often don't work the way homeowners want them to can be found at http://icwdm.org

If you mean by a so-called humane trap, a cage trap, then be sure to read our information on how to make a cage trap really humane. Lots of mythology about the so called humaness of cage traps. Our site has this info.

As for the squirrels, whether you wait to remove them is up to you. I would not recommend doing so unless you are worried about abandoned young. If you wait, till the young are mature then you can trap them as they come out. Details on how to determine if a hole is being used any more is also on the http://icwdm.org site under the title paper-hole technique.